I would just purchase
a piece of 10 - 12" fibreglass pipe, cut off another 12-14" of it and put on a bottom, top and get a piece of 2" and/or 1-3/4" for inlet and outlet and glass it all together. The outlet has an angle cut on the bottom of it and comes within a 1/4" of the bottom and staight up if you wish. The diameter can be what ever fits in your space. The inlet is glassed in at the side/top and can be at the angle that you need for either hull
etc. They can be custom like Blue Stocking suggests. Forget the loop hose as the water left in the exhaust line 5% will roll back to the engine
from the high spot. The idea of the water lock is to accumulate that and send it packing when the engine starts. Stepping up in size when it leaves the water lock allows for exhaust run and decreases back pressure. Do that twice and you have to great looking and operating water locks.
Good luck with it. Sold and recommended lots of Vetus waterlocks and as long as you don't run out of water you will be fine. Put in the waterflow alarms and you set.