What bikendan said - Home Depot. Look in the bath section. Sometimes they're on the end of the aisle.
I found the "rivets" they used to attach the shower stall wall to the trailer wall were in the way, so I got some fender connectors at the local auto parts store. I had to cut the tops off, but they look almost like the originals. I sliced the old ones off with a razor blade, drilled some new holes about 3/8" to the right and installed the new ones, then installed the shower guard. I found the long side would come apart from the wall while bouncing down the road with just the double side tape they give you. I used some silicon caulk on it and it's been fine ever since.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10