I couldn't find a comically large scope that I liked, or it needed external hardware and screws that couldn't be printed, so I made a pretty simple one that I think does the trick. If printing this, you'll need to print the tube (1) twice, then press both into the adapter (2) with the cross sights facing outward, then press both ends onto the tubes. Everything's a tight fit, so you may want to scale the tubes down by a percent or two. Otherwise, everything fits well and doesn't require any gluing!

FlashForge

Creator Pro

Yes

Yes

.16mm

15%