cephalocereus senilis

I tried to find seeds of Cephalocereus senilis online but it seems there are none available anywhere.
Does any one know the reason?
Maybe a change of name?
Does by any chance someone on here cultivate this species?

These ones come up for sale quite often through Bunnings. They take a very long time to reach flowering maturity. I know of a very large one (approx 2 meters, multiple arms) near where I live but I have never seen it flower.

Sometimes the seeds also come up for sale on e-bay.

Oh wow!  I'd love to see that cactus!  
Unfortunately Bunnings is not a fan of proper name tags. I simply assumed that what they are selling would be Espostoa lanata (the Peruvian old man cactus) as I can't find Cephalocereus senilis (Mexico) anywhere.  But I can't really tell.  Pictures are just so varying that one might think these 2 are getting mixed up a fair bit.  The main difference in appearance ought to be that the Peruvian Old Man does have sharp spines.  The Mexican does have spines too but so ???.  I'll have to take another look at the Bunning stock :-)  Maybe I am lucky after all.  I'll keep you posted.  Thank you!

Bunnings is very slack on species tags but that's probably the wholesalers fault for not providing a labelled product to them.

I bought this from Bunnings about 4 years ago. I thought i was a cephalocereus for years but when I posted a pic on-line I was informed it was a species I had never heard of before. After a bit of my own research I realised I was wrong. Turns out it is an austrocephalocereus dybowskii.

This picture was taken shortly after buying it. Its 50-60cm tall now.

Hi Sterncactus,
General nurseries here (Sydney) also sometimes get them as part of a mixed lot of cacti. They hate overwatering, so often end up dead - you need to get there quickly when a batch has come in. They are difficult to mistake for others cos the hair is quite cottony and coarse, if that makes any sense. If you are still having trouble in a month or two let me know and I will try to pick up one or two for you and post them up. (No guarantees cos they are not always in stock. I think they are Paradisia plants or else from Hamilton's World of Cactus.)