New 18650s are easily obtained (along with a range of USB-powered chargers) from:
https://www.fogstar.co.uk/ *
FWIW, I've dismantled several 'duff' notebook/laptop batteries over the last couple of years and have found that these often yield perfectly good 18650s. Care is needed in refurbishing them (a judicious application of 120-grit abrasive paper smooths down the sharp edges once the spot-welded interconnecting strips have been pulled off ... and I choose to apply replacement heatshrink sleeving as the original often tears where the cell is glued to the plastic housing). These are a good companion to the single-cell LED torches that are also available from the above supplier - a practical and inexpensive gift with the added feel-good factor of having recycled/repurposed something that might otherwise have gone into the local transfer depot ...
Guy
* No commercial connection, just a satisfied Customer.