We don’t want to do tile. We’re looking for something that is easy to maintain to main

If Kohler makes a cast iron shower receptor (pan) in the size you need, I highly recommend considering it. Solid, sturdy, well made.

Home Depot sells a Swanstone pan with those dimensions for $375. That's a sale price, supposedly it is normally $420.

If yu want easy clean and that size go Maxx acrylic one piece , totally easy to clean affordable and no chance of leaking ever. I have one a bit larger in my bathroom and it is 18 yrs old still loks brand new and so easy to clean

cat_mom: "If Kohler makes a cast iron shower receptor (pan) in the size you need..."

It doesn't. I have a Kohler Salient cast iron shower base but it's only available in 60" lengths.

Build.com is a good source to see everything that is available in one location. Use this link. Here are some examples of bases.

https://www.build.com/shower-bases-walls/c109663?facets=at_length_ds:low:36~at_length_ds:high:36~at_width_ds:low:36~at_width_ds:high:36

wdccruise, they make a 48” x 36” (The Purist which is the one we have), but still not the right size for OP. Kohler