I did this for a Samsung drive but it's probably not too hard to modify it for others.
Materials:
Perspex/acrylic sheet approx 15.2x17cm (sorry bout the metric

)
small wood screws or clear drying glue
small nuts and bolts
Tools:
cutting tool (ie: jigsaw, bandsaw or hand cutting tools)
drill and drill bits
electric sander (optional)
step 1: Disassemble your X360 and take out the DVD drive then take out the 4 small gold screws on the sides and slide off the lid.
step 2: Measure your drive and cut out perspex/acrylic, my measurement came out to 15.2x17cm and also covered the 4 holes for the case screws.
step 3: There should be a total of 8 holes you have to drill, the 4 case screw holes and 4 smaller holes where small plastic pins slot in, measure mark and drill these holes, check your measurements through and through and make sure your drilling the right spots.
For the plastic pin holes drill with a drill bit to exact size if you can so that they slot in firmly and hold, The screw holes need large holes that fit the plastic lugs on the lid.
step 4: Using 3mm perspex/acrylic cutout 2 pieces which will hold the spindle in place, you need to cut them no wider then about 50mm or it will jam your drive, one of them has a 35mm hole and the other 45mm. you can use circle cutting bits for a drill to do this, get them at your hardware next to the drill bits.
The 35mm holder needs to be at least 2mm thin so if you can get 2mm or less plastic then use that, otherwise you can do what I did and sand it down to 2mm/1.5mm.
step 5: drilling the mounting holes if your going to screw mount, drill holes in your 35mm holder that are smaller then your screws so that you can thread the holes, drill snug fitting holes in the 45mm holder for your screws so that the screws can slide in and out freely.
For gluing, glue the pieces together and make sure they are centered.
step 6: measure the center of the spindle in your DVD drive and measure and mark that spot on your perspex cover then line up the 45mm holder centered to that spot and mark the holes to drill out for the screws then drill them out again same size as the 45mm holder and countersink them for the screws.
step 7: take the spindle out of your old cover and transfer it to the new cover and screw together. the screws will most likely poke out, you need to file or trim them back flush, do not let them poke out at all or they will scratch your disk.
you now need 4 small nuts and bolts to screw that bottom half of the casing onto the drive, after this assemble all together.

Hacked out notches to fit in the case
when fitting this back into your box you may need to trim plastic off the inside of your case to get a good fit I will show some pictures of the trimming i did soon.
sorry about the crudeness of this tutorial, I am happy to answer questions and I will modify this tutorial over time.