Reflectors are made of specular aluminum, which you can buy from a sheet metal company. You should be able to find one who can get the material and fabricate a reflector for you. I think the specular (reflective) surface tends to crack when the metal is bent, so they should buy a little extra and experiment with the best way to bend or fasten it. Or to save money you could just buy the sheets, drill a few holes, and use separate strips of metal to fasten them.

It might be more practical to just have reflective grow-room walls, perhaps lined with mylar or Foylon, and let them distribute the light for you. I lined a room divider with Foylon to pull in light that otherwise would have been scattered around the room.

That bulb doesn't really require a reflector...But if you still wanted to use one I'd opt for a store bought. They will be much better, IMO......

Good Luck.

Lacunosa, what are you trying to grow?

Have a 600W Gavita over a space about 7' x 9'. I can see that the light is really dispersed, but have a plumeria in bloom with another one coming, a blooming passiflora, and brugmansias also growing well toward blooming. Have other things that are burning from too much light. Really need all this space rather than 4' x 4'.

The white walls reflect a lot of light, so that must help. The relective material on the walls suggested by nygardener sounds like a good idea. Would increase your growing space, and we all need more of that.

I have just finished a green, leaning against the house, and here are the relevant details:
1) 2 sides are exposed, one wall and the rooft, and I use twin-wall polycarbondate sheets.
2) The remaining walls are bricks.
3) Location: southeast; shaded on top; but winter sun will shine at an angle.
4) Size: 14 feet x 6 feet deep x 8 feet height.
5) I am thinking of using 1000 watts high pressure sodium to supplement the sunlight. About 100 days in a year are either cloudy or rainy, hence no sun.
6) Purpose: mostly orchids - about 100 of them; how I have a few tropical plants: kafir lime, lemon grass, hot thai chilli, and may add a few leafy stuff. But orchids are my main concern.
I have no experience with lights. Can anyone suggest some good reliable sources for certain models that I should be looking for?
I am in no rush since I won't need light until the autumn. I am planning ahead. Any relevant suggestions would be greatly appreciated.

I am leaning toward high pressure sodium instead of Halide; or I can go with switchable one. Am I on a right track?

Thanks for your help.

P.S.
I have posted the above message in error.
I forget how to delete it. My apology.

Try this http://growtechdiy.weebly.com/how-to-make-diy-hps-reflector.html