For anyone looking to DIY convert a camera to full spectrum or infrared the inexpensive route for the sensor filter is to make it yourself.
For a full spectrum conversion you just need a skylight or protective filter in a size that will be big enough for your sensor filter. With a coarse diamond hone it is possible to sand glass to shape. On the Hoya filter I used there was a snap ring holding the glass in place. On other filters a lens spanner will remove the glass.
The sensor filter in a Fuji x100 is 28mm x 22mm. I used a spare 52mm Hoya filter (I have many of them) but it was dramatically larger than I needed and took several hours to sand down. I wet sanded it with a trickle of water on the hone to keep it clean and contain the mess. A 39ish mm filter would have made the job much quicker. After the filter is sanded to size bevel each of the edges with the hone, it will make it easier to get it clean.
Make sure you get the filter very clean with no drying marks on it or they will show up in your pictures.
x100 with clear glass filter
I also did this to make a 850nm replacement dust filter for a sd Quattro H. I used a 40.5mm Rocolax filter (ebay like $12) and a lens spanner to remove the glass and then sanded it to shape for the filter holder inside the camera. Green L IR filters (amazon) are also very inexpensive and work fine.
sd Quattro H internal 850nm dust cover