Sti levers? Right hand dead

Hi all. After a year or so of sitting in the shed unused, and some very cold weather, I dragged my old (early 2000s) road bike out. And the right hand Sora 8spd sti shifter isn't playing ball. It will shift a little bit, but then it won't go anywhere. My suspicion is the ratchet, and I'll be taking the shifter apart to see what is going on. If its broken beyond economic repair (and I suspect it will be), what can I replace it with? I have no desire to move up to 9 or 10 speed, an want to do this as cheaply as possible. I am trying to find a direct replacement second hand on ebay, but if I can't what are my options?

I presume that I have to go shimano. Can I go 9 speed or did the shift ratio change slightly to accommodate the 9 speed cassette?

Thanks.

I can't remember which one, but some of these shifters are sealed. The grease dries out and they don't shift. I fixed some, not all, by flooding with WD40. You need to get the straw behind the brake lever, between the shifter. Keep them upside down and carry on squirting until they flood, then work the shifters until they free up, sometimes they need leaving overnight.

Many thanks to that man. Just WD40'd it now, and its working!!! YAY!

Yay a result Gotta love WD40, it should be one of the seven wonders of the world