Looks like you'd have $43 wrapped up in just those flanges and glass; with the other pieces, I think you'd exceed the cost of just buying a sight glass. I know that's not a very DIY response but DIY doesn't always make sense either.
Another concern would be what is the diameter of that glass (flange seems small when looking at the bolt placement). Also, how would you seal the glass against the flange?
In comparison: http://www.brewershardware.com/TC10SG.html