Does anyone know of an 8052-compatible derivative that is either OTP or ISP (preferably ISP) with at least 512 bytes of additional high-speed RAM on-chip?

I have a project that requires only around 384-512 bytes of memory--it's too much for just the 256 bytes of standard IRAM, but not really enough to justify any amount of XRAM that requires additional circuitry.

So far I've found MCUs that are ISP and MCUs that have some amount of additional memory on-chip, but no good combination of both. The Dallas DS87C550 is a little too expensive and has more RAM than I need...

Thanks,
Craig Steiner