I am working through the conversion of my PM30 and needed to do something with the Y axis to keep chips off the ballscrew. I looked all around for pre-made bellows but they are pretty hard to find and usually absurdly expensive. However, Tormach sells replacements for their mills and their prices (on the bellows) are quite reasonable. They are here on their website (under replacement parts).
Interesting fact, they sell them for the front and the back. I ordered one of each. When I got them they were marked with the different part numbers, but there's no discernible difference between front and back. However, the front ones are $10 more. So just get 2 of the rear ones, and save some money.
They take a bit of modification, but it can all be done with some tin snips and a Dremel. I just used some scissors (before I wised up and grabbed the tin snips):
Attachment 245752
The front and the back are pretty much the same in terms of what you need to modify. They are made to sit up a bit higher, and for wider dovetails. I wanted mine to sit much lower since I needed it to clear my oiler fitting. I just cut the plastic down so they sat closer to the base. I drilled two holes in the front (and back) of the saddle to mount them, and made a plate for the front to mount:
Attachment 245754
This also has the added benefit of covering the coupler for the Y as well. This was my first real part made on the mill, so it was pretty exciting. The rear just attaches into the column, no plates needed. Here's what it looks like from the front:
Attachment 245756
And from the side, showing the front and back bellows. They do a great job of catching chips, there's no real way to get chips onto the ways, other than lifting the bellows up and shoving chips under them. They come down about 0.25" to 0.5" below the ways.
Attachment 245758
All in all, the Tormach bellows ended up costing less than $50 and took just a few hours to modify and install.