Advice for a new shock PLEASE

[Tedebear]

Hey,

I'm looking to buy a new shock for my RMX 250 1990.

I've seen one on e-bay for a 93 but don't know if it will fit. plus the guy says "visually inspected" makes me iffy to buy it.

So my question is do you know what kind of shock will fit my bike that I can buy brand new ? Company or link to where I can find this shock new? Size of the shock or specifications I am looking for ?

I would greatly appreciate all tips and advice !!!

Thanks allot,
Tede