OK Bill
If you can't find any usable SD Cards, why not back-up some of your 'less-used' cards to a folder on your PC. This will release some cards for further use.......
I periodically back-up all my SD Cards to my hard drive, and because I'm a bit paranoid, I also copy them to CDs!!

I would love to cross 'The Pond' again - and have an open invitation from my good friend Bob Hendershot in Tennessee - but I'm afraid the cost is now prohibitive and I just couldn't cope with the hassle involved in flying........