Having done vasectomy teaching over many years, we have seen several different ideas for simulating the fascia which surrounds the vas deferens.
Latex tubing makes a very realistic vas deferens. Given its low cost and firm but flexible texture, latex tubing makes an almost perfect vas.

A good size to simulate the average human patient is 1/8 inch (3.2mm) outer diameter, 1/16 inch (1.6mm) inner diameter, and 1/32 inch wall. This tubing size is easy to buy online.
Various synthetic tissue has been used to simulate fascia. A condom is wrapped over the latex vas is quick and easy, and can approximate the feel of fascia.

Even more realistic in terms of size is a simple 1/4 inch diameter Penrose drain.

You can just insert the latex tubing into the Penrose drain and simulate the vas in the fascia.

Using the Penrose drain, all the steps including occlusion of the vas can be practiced. Below a young physician demonstrates cleaning the fascia from the loop of vas.

And below the physician demonstrates a fascial interposition using suture.

Even more realistic is grafting tape, as is used in joining a cutting of a branch to a tree during grafting in orchards. This tape is easily available online.

You can roll a strip of grafting tape onto a smooth table.

Then place the latex tubing on top of the strip of grafting tape.

Then just roll the tubing over the grafting tape, thus covering the tubing with the tape.

If you have rolled the grafting tape over the latex tubing tightly, this makes a very realistic simulation of the perivasal fascia.

When used in a good scrotal model, the grafting tape can be used to practice fascial interposition in a simulation that feels and looks quite realistic.

For a very inexpensive model, the grafting tape can be used in the “bicycle inner tube” model. This can allow repeated practicing of certain steps (like fascial interposition, for example) without damaging the skin of the more expensive models.
