For that size, I often get a custom one put together by a local Tin Shop, often they can make for what it cost in materials.
I then spray paint it myself.
For labels and legends, I get reverse engraved lamacoid. This creates a smooth surface where the legends are and can be any colour of legend, mixed if necessary.
Max.

 

for plexiglass, or even for that matter wood, i think there are shops with laser cutters and laser engravers
and if one isn't too particular about it looking black and such
elaborate text and artwork can be laser engraved on them to high precision

and for that matter if the particular shop has a powerful laser cutter they can both cut the acrylic sheets (e.g. say like 2-3mm) all the openings, holes and engrave them to high precision. after getting them back, all the holes, openings etc are ready and what's left may be just to assemble things with machine screws etc

but otherwise i'd think for the low cost and easy cases, a marker pen may be all that is needed and simply write the labels / text directly on the surface

 

My mechanical engineering partner wants to try to weld the sheet metal together but I like the idea of making a frame out of the angled aluminium first.

Doesn't the enclosure have to be water tight?

Also, Harbor Freight sells a hole knockout punch set that can make clean holes in aluminum and mild steel.

 

Doesn't the enclosure have to be water tight?

Also, Harbor Freight sells a hole knockout punch set that can make clean holes in aluminum and mild steel.

Water tight is preferred. We plan to silicone most places to achieve this. The only places we are concerned about are doors that allow access to the battery and electronics.

 

Here is an example of one enclosure I had made at the tin shop and I sent a DXF file for the Lamacoid to my engraver and he reverse engraves and adds (any) colours from the back.
Creates a smooth surface for the panel and legends.
Max.

 

Water tight is preferred. We plan to silicone most places to achieve this. The only places we are concerned about are doors that allow access to the battery and electronics.

That would be a NEMA 4X rating or higher.
https://www.siemon.com/en/home/support/compliance/nema-ratings-and-ip-equivalents
Max.

 

Here is an example of one enclosure I had made at the tin shop and I sent a DXF file for the Lamacoid to my engraver and he reverse engraves and adds (any) colours from the back.
Creates a smooth surface for the panel and legends.
Max.

Your engraver misspelled "center" - TWICE! I'd ask for my money back!

 

Your engraver misspelled "center" - TWICE! I'd ask for my money back!

He spells it the way according to my DXF file.
Having had a British upbringing it is a matter of habit.
Also for a Canadian customer.
Max.