On several year models, including our 2001 Marquis, there is a chrome plated screen door handle that likes to get caught when the whole door is closed on it.  The handle bends making it hard to operate.  I found a source for replacements.  RV Designer Collection.
http://www.rvdesigner.com/catview.asp?ci=10&cs=1
The part Number is L559 under the Exterior Hardware tab.
On the same page is the bay door latch Part Number E523.

After you locate the part you want, click on "where to buy", click on your State, and select a dealer near you.

Larry