WOW!
I'm amazed about the number of replies and the quality of the suggestions I got.
First, to clarify the kind of snorkel I was talking about, here is a link to the Finis product description:
Swimmer's Snorkel | FINIS
It's meant for swimmers who want to concentrate on improving their stroke and it makes it unnecessary to move their heads sideways for breathing. I got it with the idea that it will allow me to stay just below the water surface for some time, observe the wildlife and perhaps take a few pictures. That in itself would be a big step forward for me. But, as has been pointed out, this is snorkeling which is a completely different kettle of fish from diving....
As far as the mask is concerned, I had so far not considered the option of ordering it from the US. Receiving goods from abroad is a bit of a lottery. It might or might not get held up in customs, there might be some delay before I am contacted, and there is no way of knowing in advance how much duty I'll have to pay. On the other hand, those shops that import the goods for you slap a 200% markup on the US retail price. So you have the choice between a rock and a hard place.
But, as there were several suggestions in that directions I followed up the links and e-mailed scubatoys.com with some questions. It turns out that the range on the Mares X Vision only goes to -7.0 whereas I need -9.0 on my right eye. There is also the Tusa mask (I didn't like the look of) that goes up to -8.0. The ideal way for me would be to order the mask with the lenses already fitted, but that would mean I didn't get the chance to try on the mask before I bought it.
At least one shop operates on the basis that I send them a mask I bought locally with the position of my pupils marked and the send it back to me with the lenses fitted. But I'm having a hard time finding any kind of mask in the sports shops in Rio. It is famous for its beaches (and the creatures that populate them), and has an active surf culture, but I don't know of any diving spot around here That may account for there being no diving gear in the shops.
In short, there are just too many uncertainties involved in the importing option. I may be going to a lot of expense and effort and still end up with something that I can't use. So I have decided that I won't be doing my "Baptism" dive this time around. I'll talk to the diving instructors to see if they can give me a few hints on where in Brazil I can get a mask for my requirements (and my wallet). I'll do some snorkeling, which I'm sure I will enjoy, and I'll climb a few mountains. There may still be another chance for my first dive. I think it's better to take thinks slow and easy rather than rushing it and be disappointed, or worse.
So, thank you all for your input. You helped me understand what's possible.
Gato