As photo bucket is acting up and I've yet to set up another photo host, I can only describe the two "Stargates" I have in resin .
The largest of the two has a outer diameter of 19.5cm iner diameter of about 13.5cm in white resin details on one side only.
The 2nd smaller one is in black resin/plastic outer diameter of 12cm iner dia of 8.5cm with again detailing on one side only,it comes with a platform 3cm high 7.5cm at the widest point, the design of the gate has a number of stairs up to the gate which slots into a gap in the platform.
Both where bought via eBay via I assume buyers with access to a 3Dprinters and the right file - cost about less than £10 each