The simple Chinese colon tubes are available in at least 4 lengths, 50cm, 100cm, 150cm, and 200cm. IMO they combine about the right combination of stiffness and softness for good insertion. They are a bit softer than the vintage Davol or BFG ones, but seem to work fine. The Fr36 size is a bit bigger than the old Davols, most of which were Fr32, but the larger size is not uncomfortable. Remember, a normal adult poo is roughly Fr90 (1¼")
Inserting a colon tube requires some skill and good technique and, most of all, a very gentle touch. If the recipient is full of hard poo, insertion probably won't be easy. In such cases insert the tube a few inches, then start the enema to expand the person's colon. Then gently advance the tube until it's fully in. I don't find the absence of side holes a big detriment because a colon tube should not be pushed into a lump of soft poo, hence clog.
A real plus of these tubes is that they are made of silicone material, rather than natural red rubber, which means they can be used with a lubricant like Vaseline which makes rubber perish. Using an oil based lubricant makes inserting a colon tube high easier because the lubricant doesn't wash off the tube if you run in some enema water to aid insertion.
BTW, some come with adapters to connect to a Shower Shot. IMO, these are dangerous because there is no pressure limiter. IMO, these tubes should ONLY be used with a bag or Higgenson pump