try this...
get a small square of plywood. If your "transparent dome" is say, 4 inches in diameter, get a 6" sqauare of plywood and cut the 4 inch circle out of it. Now get yourself some smoke tint acrylic probably bout 1/4" id say...and heat it up in your oven.
now your best bet is with that square make a little box that will hook up to a vaccumm. Like with the hose connection. Once you have a sweet little vac box, get that acrylic nice and hot and flimsy. pull it out and set it over the hole, and then turn the vac on...but turn it on in spurts...and that should give you your semi transparent dome.