Welcome to the forum.
Without going to the expense of have a new one fabricated, I'd suggest two things first and I'm sure others on the forum will have better suggestions too.
I'd first see if it can be repaired. A shop that specializes in fiberglass repairs could give you their advice if it can be repaired and maybe an estimate on what it would cost. If not a good shop that does a lot of RV body work, find a shop that repairs boats. One good thing is that you can remove the door and take it to their shop and let them evaluate what has to be done, if it can be repaired at all, without having to drive the motorhome to them.
There has to be a lot of marine fiberglass repair shops in the Vancouver BC area. A very good one to check that list RV repairs too, would be:
MRV Marine Services ----->
website, go HERE
17832 96 Avenue
Surrey BC
778-858-3202
marinerefinishing@gmail.com
The other suggestion would be to hunt around at various RV salvage yards. For example, I see that there is currently a 1998 Dolphin that is being salvaged for parts at Visone RV, a prominent RV parts vendor in Kentucky. If a match for what you need, they could probably send it to you in Canada.
PARTING OUT - 1998 NATIONAL DOLPHIN. FRONT CAP, REAR CAP, BASEMENT DOORS - Visone RV
Visone contact page and where you can go to check if other 1998 Dolphins are being salvaged in the future,
go HERE
Also know that iRV2 has a
National RV Owner's Forum too if you'd like to post or ask for specific information on things that National owners might know and be able to share ...
go HERE