Is it possible to replace the bed on my 2005 ford ranger XLT Supercab?

Sure you can You can ,if your mechanically inclined even a lil bit .You can do it yourself with the help of a friend Or send it to a body shop i suppose they could even source the bed for you I have seen them go for around 500 bucks ,You may want to check local truck body builders When they do remove a bed from any truck .They usually keep the bed after installing a flat bed or utility body .So that may be a be a place where you can find a clean one But of course a salvage yard will most likely have it too .But it may be really rough condition But yeah you can ditch the "style side" cr@p for a standard fleet side bed

Auto Recycler/ Junkyard or a body and paint shop.