Bicycle Mechanics - STI upgrade ... needed? ... recommendations?

My 9-year old bike with 8-speed Shimano Ultegra STI shifters has been giving me shifting troubles that tell me the chain / cogs are worn (again) and the rear derailleur is probably worn out. The mail order places don't carry any 8-speed stuff anymore and my LBS doesn't have much. So it looks like planned obsolescence has won and I may have to upgrade just to get parts. Can anyone comment on the availability of 8-speed components? Do you know a source of parts?
IF I decide to upgrade, should I go to 9-speed or jump to 10-speed? If I recall, the dropout spacing is 130-mm for all three.
Thanks!

Ebay..

What he said ^^^^^^^.

Plus Google the name of the individual part.

Less 8 speed (unless you like SORA) more 9 speed. Ebay is you best bet, but a 9 speed upgrade might not cost all the much. STI 9 speed shifters and a new chain and rear cassette. Your cranks and front and rear dr should work.

A rear derailleur from any 9 or 10-speed group will work fine with your 8-speed shifters and cassette. Finding the cassettes is a bit of a problem but they are still out there. 8-speed chains are readilly available and a 9-speed chain will work too.

If you want to upgrade a bit, 9-speed 105 components are selling at bargain prices right now since 10-speed 105 has been introduced. 9-speed components should be available for a long time to come too.

Nashbar has 8 spd cassettes for $19.95. Available in 11x28, 12x32, 12x28, 12x21 or 12x23.

Actually, an 8spd derailleur will generally work with a 9spd STI shifter, if you let the low limit out a bit. I really doubt your rear derailleur is worn out, I think I have actually seen one derailleur that was truly "worn out". If you go 9spd, get some Tiagra/105 9spd shifters (work great + cheap), keep your rear derailleur (maybe get new pullies?), and replace the cassette + chain.

Convert to friction/ratchet barcons and stop sweating component compatibility.

Barcons are a great option, that is what I use anymore.