<-- This one has TONS of great stuff! Bridles, bits, fly masks .. everything except saddles! Duett Saddles: The Partnership of Horse & Rider
<-- Wide gullet saddles. Pretty popular, but they run around $1000-1200 new + shipping. I bought one for my Perch mare, she's a 36 gullet and we love it. They go all the way up to 44! (The average gullet is 28-30). You can usually find them on eBay and forums for sale for quite a bit less. Fine Equestrian Products at SkylineEquine.com - Quality English Tack Supplier & Manufacturer
<-- They have a plain old snaffle bridle in draft size (it was actually too big for my girl in some areas - had to punch holes to make it smaller!) for about $40 Canadian. Not top quality, but it does the job and it's really sturdy, and looks nice!
As far as her fear and disrespect .. that's a tough combo! If you have a roundpen, I'd really get her working. Even if that means less than ten minutes per day for now. I assume you know basic roundpen work? Transitions, switching directions, etc. Get her listening!
As far as getting her out of your space: Get. Her. Out. Of. Your. Space! Ask, tell, make it happen! If Rosie won't back up? Ask her nicely like you normally would. Then ask harder - swat on the chest, etc. Still no reaction? Get her attention! Yell "HEY! BACK UP!
", flap your arms, shake the leadrope, stomp at her, whack her with the rope. Scare the crap out of her, make her WANT to get away from you! As soon as she moves away, release ALL pressure. Stand there quietly. Then, ask her to back up again. Rinse and repeat, until she's moving off when you ask her nicely. You might have to get pretty physical at first, depending just how unwilling Rosie is to listen. Once she's moving away from your pressure, her respect should start to build in other areas - if she tries to drag to around while leading, give her a sharp snap on the halter. If she doesn't listen, get her circling on her hindquarters away from you until she's pretty much dizzy. Try leading nicely again. Doesn't listen? Do it again! She'll get the idea. Percherons are smart.
With a horse this size who knows just what she can do, you have to match her level. If she's getting pushy, you have to get pushier.
I know that my mare became spooky when she lost her trust in me and I failed to show her that I was in charge. Not quite as far as yours, but I know there was one day where my mom's shoe scraped on the ground and my girl literally bolted. It took just a few rides where I really made her realize that NO, that's not something to be afraid of, and YES you're going there, and YES you're going to listen to me - and bam, she started to steadily improve. That was a year ago. Now she's **** near bombproof. I'm not sure if it's the same situation with you, if it's just a complete lack of trust, or something deeper (abused at some point?). It's not the nature of a Percheron to be that fearful. They are intelligent, yes, and more sensitive than the other draft breeds, but not to that point.
Good luck! I'll go dig for some more draft tack websites, I found tons when I first bought Delta.
EDIT: As far as the bit goes, I'd hold out until you've done some work with her. You may find that as her groundwork improves, she won't need as harsh of a bit as you think. She could just need a wake-up call! If she still needs it, fine, but you wouldn't want to overbuy, either.