[Fixittt]

Jay is on the right track. IU would recomend getting a peice of solid acrylic round that is the same OD as the tube, and have it machined so that it will fit loosley inside the tube except for the top (with a lip towards the top so it sits flush and looks professonal) and machine 1 or 2 o ring groves in it.

Acrylic is actually very easy to machine. U just need to have your cutter at a slow RPM so it doesnt melt the plastic. I am willing to bet that your friend can do this in his shop. Just tell him to bring down the RPMS alot. Its like machining any kind of material. Make sure you are getting chips, and not dust or melted plastic.

Also when machined at the right speed, acrylic stays clear. If wd 40 is used as a lube when machining it stays pretty much crystal clear. If it is still a bit frosty colored, you can either flame poish it, or sand it with very high gritt sand paper with wd 40 as a lube.

Your top shouldnt be that hard to do.

Hope you get what U want