These tubes are nothing special. Any plastic tube of the right diameter will do. It should be wide enough to sit on the top of the slot where it widens. Cut it to length and then cut the end at about a 45 degree angle. This is simply so you can get your finger in the tube to hook it out.
Is yours a 10x8 slot processor? If so I or another user can give you the measurements of length and diameter. A hardware store that keeps plastic tubes should be able to supply them