These are pretty boring specs these days, especially if 100 MHz is enough. That's not fast.
You don't say whether you want a chip or a board. Often a chip on a board doesn't actually cost any more.
As others have said, in the Arm world the Teensy 4.x for about $20 simply kills those specs with 600 MHz (overclockable to 960+), 1 MB SRAM, 2 MB flash.
But that's old and you can do better now. e.g. for $5 you can get the Milk-V Duo, a 1.0 GHz 64 bit RISC-V running full (command line) Linux in 64 MB of RAM, plus a 2nd 700 MHz 64 bit microcontroller core. I don't remember how much SRAM is available for the microcontroller to run from, but it's far more than you asked for.
You can, if you want, edit and compile your code on the board itself (via ssh or serial terminal. Pop the binary for the microcontroller program into a special directory on Linux and BOOM! it's programmed.
For $5!
Heck, even the very first RISC-V chip for sale in 2016, the SiFive FE310 on the HiFive1 (also available bare for $5) ran at 320 MHz with 16 KB data SRAM and 16 KB icache (reconfigurable to a split icache/ITIM in the 2nd revision). The HiFive1 had 16 MB of external SPI flash for the program.
You asked about Arm, but RISC-V has very little practical difference, even if you want to program in asm.