I'm a dry camper too, so this is one of the first things I did. Those 921's drew lots of amps, and were HOT! Want to warm your trailer during winter...just turn on the lights.
I bought mine off ebay. Took about a week to get to CA from China. Never had a problem with them.
Here's who I bought them from.
I'd suggest the round, direct plug-in type (pictured) as opposed to the flat, stick on type. The round ones are easier to pull and put in a new RV when the time comes. The flat sticky ones are a bear to remove.
Also, I'd suggest getting the regulated LED's. You can do a search on "LED's burning out" and see what they say. Ebay ads for non-regulated will say "12V", while regulated LED's will say "12-24V".
Lastly, color. Warm White is like your traditional incandescent bulbs at home. Cool white has a blueish cast to it. Not my cup of tea.
Here's the difference between the two-
Non-regulated
Regulated
Rick