I'll try to answer some questions, hope I get them all.
The projectors are a variant of the G8 projector. They have a different shroud but the internals are the same. The bulbs can be purchased by searching for "G8 HID bulb" or something similar. Keep in mind, that on the 35W ballasts these bulbs are rated for 3200 hours, and on the 55W ballasts ~1900 hours. If you drive two hours a day, you are looking at 4+ years on a single bulb. You can also extend the life of them by disabling your DRL. Of course, anyone who needs extra bulbs at some point and is having trouble can contact me and I can either supply them or point them towards various websites to get them. The reality of any aftermarket HID setup is that you will have to order bulbs online. AutoZone just does not carry anything of the like.
The pricing on the Golf will be +$20 over the jetta. The Golf headlight assemblies just cost more from the manufacturer.
The "GLI" style golf headlights are significantly more from the manufacturer. In the range of $30 more over the chrome. It is dumb, but it is what it is. For that reason I would generally stay away from those. At some point it started to get away from the affordable concept. I think part of the problem is that the black lip golf headlights are so called "20th Anniversary" lights, so for some reason that puts a premium on the look. I think that is nonsense, but I don't produce the lights so I can't change that. That being said, if a customer really wants them we can make it happen. I can either just order the black ones at whatever the additional cost is, or I can paint that lens lip myself. I would charge maybe $5 extra for the cost of paint but that is it. I would not like to get in the habit of doing paint jobs to these, so I won't offer them as a normal thing, but if someone is that set of them I'll do it.
Almost forgot, The lens diameter is 2.5".
If you guys have more questions let me know!
Jeff