I have a well bred 'toy' breed boy, I researched my breeder well and approached before she had a litter, I was added to the waiting list and when he arrived he was mine. Don't count yourself out! Most reputable breeders will be very happy to help someone just starting out as long as your responsible and can care for your new addition.
I picked out this reply because I have to agree, especially when it comes to males. Most breeders, whatever the breed, tend to want bitches when they breed, and can only keep a limited number of males, if more than one at all. So provided you state your intentions, want to show, I'd hope most breeders would welcome you with open arms when it comes to letting you have a promising male. Not however, you may be better to save up and hope to buy one that has matured a bit - perhaps one that was 'run on' by a breeder so she had more time to make her choice. Assuming more than one is good enough to show! I bought the one I have now, at the end of my own bloodline, at 4 months as a show potential - unfortunately that didn't work out as intended!! So I have a lovely pet (which all my shows dogs were firstly) with show faults!! If you buy a slightly older pup, it might be better given your situation with a bigger dog there already.
As for when and where to approach a breeder - whatever you do DO NOT approach a breeder before they've been in the ring!!! And if she's been thrown out with the rubbish, it might be as well not to bother then either!! I went online when I decided to try another breed and found some breeders reasonably locally, phoned them and went to see a couple. Could be because I'd been in my main breed for ions, but I was welcomed - and was even given the chance to pick the BITCH I preferred, of the 3 she had. It so happened she was keeping a male from that litter, so that worked out well.
Some breeders are more open to genuine enquiries (show) than others, and indeed, some breeders in some breeds are more welcoming than others. Don't give up if you get rebuffed at your first attempt!!! That relationship would never work in any case and you do need a mentor with a new breed and getting into showing within that breed.
I would just say that getting into my main breed, all those years ago wasn't plain sailing really. There happened to be a major breeder quite close and I thought I liked her stock so bought from her. No choice, just 'this is your male puppy'. Fine. We thought we had the next Crufts BIS on our hands - until I started taking him to some small local shows. Reality kicked in. Well bred pet and that was all. During that first year, I'd joined the Breed Club and met up with a fellow exhibitor who bred the occasional litter. She had a lovely male puppy out and over time I persuaded her to do a repeat mating, with me being allowed to have pick male. Actually as often happens, he really wasn't much like her puppy but we did, having skipped the Pond, show him in Canada and he took a Can.title. Having ended my bloodline, when I looked for another of my main breed, finding one I liked proved difficult - but then I'm more picky now than I was with our first one!!!