Replacement for IDT70825S/L: Sequential Access / Random Access Memory
I'm not too deep into the varieties of RAM there are, but if you just need the random access method, any SRAM will probably do, as 25MHz isn't really fast by modern standards (and faster SRAM will still work at slower speeds).

If you need the automatic sequential access: a small PAL or FPGA between RAM and controller will probably do the job of increasing the address you're talking to. However, you'd need to write some HDL to achieve that. Again, 25 MHz isn't fast, so even an ICE40 (for which a Free &amp; Open Source toolchain exists) will do the job.