Finding a hardtop for the aft deck could be a challenge. You might try some of the salvage yards (mostly down in FL) to see if they might have something from hurricane-damaged boats.
Otherwise, you'd have to do a custom one. There is a thread on here where a member made his own on a 3207 several years ago and it turned out great.
That hardtop was not available on a 325. Hardtops were available on the 355, but those were attached to a radar arch and then stainless steel supports. Your best bet it going to be having one custom made. Will be pricey, unless you can find a person who does that type of work as a hobby. You may want to consider doing a sunbrella or canvas top. There are a number of possibilities there, maybe utilizing telescopic extending poles attached to the top edge of your bridge. Good luck. er
Cooler By The Lake
( All weather people have to say this on air, near lakes )