Having melted acrylic on various occasions, I can hazard a guess why FDM isn't popular with this material: not only does it give off an acrid odor, the melted material is sticky and viscous, likely too much so to make into filament or to print reliably if so made. Most acrylic materials are made by curing a liquid resin, either with a catalyst ("casting resin", used among other things to make the spherical hulls of high visibility submarine vehicles) or with UV (these are different materials, but both in the acrylic family).
The "an acrylic" that Shapeways offers, being UV cured, is most likely a SLA ("resin") print. If it's any sort of acrylic, it should still be thermoplastic, but will suffer the same disadvantages as common "Plexiglas" acrylic PMMA -- very, very stinky stuff to melt.
One thing you might consider is using the "mold" capability in Cura Slicer (not sure if other slicers have this, though apparently some mesh modifiers can replicate the effect) to produce a 3D printed mold in which to cast parts from acrylic resin sold for either fiberglass application or casting. If you start with the correct resin type, the cured result will be nearly identical to PMMA, and you can make the mold on a common FDM printer.