Ah, Air Pistol, now we're getting somewhere.
Yes, it will want to be .177
Given that you're asking after SSP rather than CO2, I imagine you're looking at 10metre rather than action shooting or whatnot.
You're looking at something the lines of an IZH46M, Feinwerkbau 102/103 or a Pardini K58 amongst others, most of which can be had second-hand for £300 or less (most new ones are PCP and start at £900). There aren't many dedicated target SSPs still in production - just a few models to service the market for affordable "club guns".
Have a hunt around in sales here and also on targettalk.org - it's got a bent towards Olympic style shooting, so the talk may be a bit more relevant than on here.
"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud
Shooting is my meditation