A friend for Crossbone

Klein Poodle.
http://www.dogbreedinfo.com/k/kleinpoodle.htm

(that site maybe not totally accurate)
A bit bigger than a mini, a bit smaller than most Standards. There are some really nice Klein Poodles in the US.

This is a breeder, whose site just happened to come up when I did a search for Klein Poodles. (so, I know nothing about them personally, just using the site for the info). Accurate info on the variety, and they do appear from the website to be a decent breeder.

http://karbitpoodles.com/home.html

I'm not sure what you mean by a good Crested breeder? They are generally either show or pet bred and like most toys, finding breeders who health test can be hard. But like you said, they're not really a sporty breed and finding a breeder with heavily titled dogs who's really active in sports might be asking a bit much. I worked with two Crested breeders for years and have been around lots of them. They're definitely not dogs for everyone. They tend to be pretty hard to housetrain and are bad markers, even the girl some that I knew would would mark with feces as well as urine :nono: ). The really pretty ones with the long feathers and mane? They're called "hairy hairless". What that means is...they're aren't actually hairless unless you shave them, so there can be a lot of grooming to maintain the look. They're also prone to skin issues and some get very bad acne. Dental issues are pretty widespread, especially in the hairless dogs and it's not at all unusual for them to end up toothless. Temperament wise they're a bit all over, since they aren't bred for any real specific purpose-related temperament traits. Out of all the breeds you listed, I'd guess they would least likely to enjoy rough housing with Crossbone.

We have an awesome mini Poodle in flyball class right now! She is ball obsessed, loves to tug and is just a great sports prospect. A Decker RT seems like a good option too.

I'd also suggest a good Mini Aussie/North American Shepherd. If I was looking for a sport dog in that size that wasn't a PyrShep, Mini Aussies would be high up on my list.