Where is Scott Dorsey or Mike Rivers when you need them...
Many recordists have built their own rigs. Various types of material can be used. What do you have laying around? All kinds of stuff have been used in the past; plywood, cardboard, sheet metal, PVC or other kinds of plastic, etc. It's really not that critical.
Even a couple of mouse pads can be glued to the above mentioned material instead of foam. It's all good. Try it out and see (hear) what works the best for you.
The AES Journal on stereophonic techniques had the original Jecklin paper. Josephson website has information on the topic too. Check it out here >
http://www.josephson.com/tn5.html
Also check out Scott Dorsey's info called, "About Our Mics" >
http://www.techwood.org/kludge/mikes.html
I hope this helped...