My bowl appear to be missing the jet in the corner of the bowl. Can they be had anywhere?

According to Partzilla, these other models used the same part (click on "Product Fitment").

YAMAHA OEM BODY FLOAT CHMBR 1 - 214-14181-12-00 | Partzilla.com

says it does not fit a 74 DT360

It's just the way the site is formatted. It looks like the model you select the part from isn't shown, so view the list as "also fits".

Yamaha Motorcycle 1974 OEM Parts Diagram for CARBURETOR | Partzilla.com

I've never ever seen one of those fixed jets escape but there's a first for everything lately on here. It would still run normaly with the choke closed, but be interesting to experiment to find out how rich starting the choke is minus that small jet.
I thought--without looking--that the pipe which extends down into there only has a small hole in the end anyway.
Unless i have my carb types muddled up.

Any DT1/2/3 carb bowl will do the trick , but may need painting .
Someone could have a parts carb lying about .

Well there ya go, I'm still learning & didn't realise dt360a had the side mounted main jet. 214 part numbers I always relate to dt1. Thanks Swoop. Ps. Hope ya not flooded out down there. Looks as bad as it gets, or worse.

Some bowls have no starter jet.
Do you know you need it?

NOS Yamaha DT1 DT2 DT3 RT2 RT3 Carburetor Float Bowl Body Chamber 214-14181-12 | eBay

Don't know for sure but the bike does not like to start with out starter fluid.