The R2 RGB would pretty much be your only option for MX Topre unless you wanted to order third-party sliders and swap them onto a normal R2 or 87U.
Reviews of the R2 RGB are mixed and I would agree that it doesn’t sound nearly as nice as the stock Topre without modification, but it’s not also quite so bad as some people make it out. Many folks here have reported good modding results to make it sound good. Most recently here. A foam or sorbothane liner on the inside of any of my housings is also a great idea, and perhaps especially on the RGB.