I can’t go to real shops to rummage in the leather scraps bins at the moment
Fortunately one of the suppliers I’ve visited a few times (both in London and North Hants) is online, though more for larger pieces (some scrap bundles):
Etsy (offers free postage if you don’t need super-urgent courier) https://www.etsy.com/shop/GHLeathersLTD
Website:
http://www.leathermerchants.com/
They are a nice lot and I have just ordered some materials for next project (more boots!)