Semi-modular Drum Machines - what options are there?

Are there any multi-voice semi modular drum machines?

Yup. Have a look at SOMA's Pulsar-23. https://somasynths.com/pulsar-23/

Ya, that’s the only one I’ve been able to find. Looks awesome but expensive :(

One other, also...but it takes two modules: https://www.modulargrid.net/e/tubbutec-6m0d6 and https://www.modulargrid.net/e/tubbutec-6equencer-3u However, this also illustrates the modular cost-spike effect as well...all of the device clones of the TR-606 come in at a great deal under the $856 that the Tubbutec modules cost.

That 6mod6 really does look sharp though...