As noted and covered before in other posts, there quite a few remains of the various incarnations of London Bridge doted around.
2 pieces of the granite 1832 bridge are now sited near Waltham Abbey, marking the Meridian Line, and called Travel and Discovery. The Greenwich Meridian website states they were in place in 1982 and carved in 1994.  
Matt Brown at the Londonist notes they were carved by Paula Haughney, the Bromley by Bow sculptor, who also carved the Cornish granite at the Middlesex Filter beds for the Hackney Henge! 
As covered by The Building London Blog previously! https://buildinglondon.blog/2021/10/30/17-natures-throne-and-the-hackney-henge/
As does Edith’s Streets – “Meridian Walk – The Greenwich meridian passes right up the centre of the site and there is a path marking it. At either end is a carved granite monument made of stone taken from the base of Rennie’s London Bridge and decorated around the base by local school children. They are called Travel and Discovery, one featuring a world map carved with 0° line of longitude and the other with a strange human form. The uncarved blocks were here from 1982 and in 1993 Paula Haughney was asked to carve them. They were taken to Abbey Gardens to be worked, and reinstalled in 1994. The carving was suggested by the Meridian’s association with time and distance. Carvings of navigational instruments on a tomb in the Abbey Church also contributed.” 
Vic Keegan identifies 3 more stones locally, at The Lea Valley White Water Centre AND 1 more in the wood where the Meridian Stones are! Can you find it?!? 
And I found a different one, which can be assumes to be f from London Bridge as it’s a big block of Cornish granite, in the Abbey Gardens Carpark and which is not on Vic Keegan’s map!
And another mosaiced stone stands just a bit further north, at Fishers Green, and there is a public footpath from the Meridian Walk to there!
How they got there is all a bit of a mystery! Keegan states that “…Bryan Hewitt, author and gardener at Myddelton house in Enfield which itself is home to bits of the mediaeval bridge… told me that in the early 1970s a load of huge granite blocks was deposited by persons unknown on a roundabout on the A10 at Hoddesdon in Hertfordshire. I would guess that they came directly or indirectly from the yard of John Mowlem and Company who demolished the old 1830s London Bridge in the early 1960s when most of it went to Arizona” 
And that suggests there will be more to find!
And Building London will keep searching!
The granite came from the Haytor Quarry in Devon, ( which Building London has STILL not visited but will hopefully do so soon ) quarried between 1825-1831.   The granite for the widening of London Bridge in the early 1900s came from the Dartmoor Quarries of Foggintor and Swell Tor and so some of these blocks might be from there instead of Haytor https://buildinglondon.blog/2021/07/31/a-visit-to-swell-tor-quarry-in-devon/ https://buildinglondon.blog/2021/08/04/foggintor-quarry/
Not only are there quite a few stones to see, at least 7, the woods are lovely and there are walks that will take you through the neighbouring Cornmill Meadows and Dragonfly Sanctuary and up and down bits of the Lea so well worth a visit just for that.  
The Meridian Walk itself runs due north, obviously, through what was once the Greater London Council’s tree nursery or arboretum – it’s not clear. Edith’s Streets states “A Tree Park, once the Greater London Council’s Arboretum. Lee Valley Park took this over. There are rows of potential street and parkland trees. Hedgerows around the site had elms growing which were killed by Dutch elm disease. Willows west of the stream were planted in 1979 and were planned to be sold to cricket bat makers.” 
And definitely though also visit the Waltham Abbey Gardens whose wonderfully mixed 12thC rubble walls, of clunch and Caen, cherts and conglomerates and beautiful old bricks, are extraordinary!   
Diamond Geezer traces a path you could follow here… 
And if that is not enough there is the only recently opened Royal Gunpowder Park with incredible history and buildings! 
A train from Liverpool Street to Waltham Cross takes less than 30 minutes and then the walk to Waltham Abbey takes a bit less. and the Meridian Walk starts opposite the car park for the Abbey Gardens.
And the whole area is a nice days cycle to and fro from London up the river Lea!