Replacement for Ice Cap RSK 16 x 36

I need to cross-reference replacements for some a/c units made by a defunct company in Long Island called Ice Cap. Their (hot/cold) model was either a 12,500 or a 14,400 BThU unit measuring 16 x 36 inches.
Does anyone know any sources for cross-referencing modern units which will slot into the Ice Cap sleeve built into the wall? Or a n/g where someone might know please?
Ice Cap mentioned that THEIR units would slot straight into numerous other manufacturer's sleeves so the reverse must be true? (The only one I can find is an Islandaire which looks as old fashioned as the Ice Cap)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.