I used to own an
acrylic business before I went cruising.
Look for a business with a laser
cutter. Any laser machine can cut 3/4" acrylic. A good shop will ask for one of the old lenses and then make EXACT copies (including all holes). It will look like it came from the factory!
Be aware that if you are only getting one made, then the
price will be very high (setup
fees, tooling
fees, ect). However if its spread out over a bunch of lenses it can be pretty affordable.
A CNC routing machine will also
work, but they usually have higher setup costs.