I have some 1/87th scale rubber rafts made by Roco Mini-Tanks. They are a little long since I think they are 8 man rafts, but by cutting a section out of the middle with a razor saw and glueing them back together, they would look OK for 1/72 scale 2 man rafts. Outside of that, get out the epoxy-putty and roll out a pencil sized log of it, bend to shape, connect the ends and build a floor out of sheet styrene. Add of straps of sheet lead and a rope around the circumference, oars and you're good to go.
P.S.: Welcome to the Asylum!