I pulled our archive materials and the ASM-2 steam bath generator was made for AquaGlass by Steamist. The steam head has a hex shape and the Steamist acrylic box (weep box) is no longer made. The steam head protruded less than 2" into the steam shower.
There is an alternate steam diffuser that would work, however; you should verify its size for proper steam shower fit. You should also verify that you can remove the steam head prior to making the purchase as the diffuser requires so. If the head is not adequately supported in the wall, removal could be tricky.
Follow this link to see the preferred diffuser. http://www.steamsaunabath.com/catalog/steam-diffuser-amerec-p-235.html