I would call around locally to prop shops and ask who still does bronze sand casting.
IF you can find a shop that works by the pound ,recast scrap is just fine.
The units shown as a Perko sucks as the corners where the line comes out are far too sharp and should have a radius closer to an inch or more.Esp if the unit will be forward and might take an anchor line.
Creating a plug for sand casting is quite simple , tho remember there will be a bit of shrinkage.
Soft pine , or even balsa painted is OK.
If you take them as cast and do a bit of filing , its the lowest cost.
A very soft radius IS harder to install, so most boat assemblers want to chop a hole with a jig saw and then plop in a nautical SS cover.
The extra work is worth it , even for just a dock line as in a blow it will be quieter below as you dont have to listen to your likes being sawed thru.
The Chinese units for larger sail boats are a delight as many have horns cast in to hold the line.
The danger of catching an ankle on the horn is worth the danger as the closeness to the tie up point means there is little line to stretch , so no sawing and no noise.
A really useful item is genuine hawse holes that accept the anchor.
The mud and gunk is never brought aboard , and the large size can handle a good gentle radius with ease.
DIY if you want the best, it may be cheaper! as well as better.