Pretty much any blade labeled for plastic, laminate, or non-ferrous metals (brass, aluminum) will work fine *enough*. Obviously some blades are better than others, my fav for the $$ is the Everlast line, but there are many others.
Do try to get the thin kerf so it's not so hard on the saw motor.
I would definitely get at least two blades. One strictly for acrylic and one for MDF, PVC, etc. These can dull a blade almost immediately making them very hard on acrylic (read; can induce crazing) and is the major problem for DIYers when they encounter melting.
You can go to FTM, as Louey pointed out but my advice is to find a local supply house that sharpens blades as well.
An *ok* blade for plastics should run $50-60, a good industrial quality about $100-125. I wouldn't even think about Forrest blades as they simply aren't worth the $$ IMO.
If you get a 10" saw and want carbide blades, get an 80 tooth blade for good all around acrylic work.
The acrylic blades make for excellent cross-cut blades as well so if'n ya wanna spring for two of 'em - is a good choice IMHO.
James