Ral Partha's a good shout, but I'd also have a look at
Tin Soldier UK. A lot of their stuff is like Ral Partha redesigned by Minifigs - very stylised and very distinctive. I think they would look
tremendous in Otus-ish bright colours (indeed, I'm painting up some of the orcs at the moment in an attempt at a similar style):
There may be a direct Erol Otus influence in there too: they do a terrific hydra (for a fiver!) that's clearly inspired by the Sutherland illustration in the Monster Manual, so they're drawing on the early D&D vibe (the figures are decades old and originally Australian, I think). To my eye, a lot of the slightly baroque shapes of weapons and armour are very Otus-ish.
It's worth noting that Tin Soldier also has the best service in the business. I made a small order last week and got it
the next day! And the figures are extraordinarily cheap (typically a quid a figure).