try tap plastics. they are online at www.tapplastics.com
there is a link to "plastic adhesives" on the left side bar of their page.
if you have good straight edges, you will need weld-on #4.
if you have rough, not too straight edges, then use weld-on #16.
weld-on #4 should give you perfectly see-though joints, provided you have good edges to start out with. if you have bad edges, you will not get a good joint, and the seam will be weak.