Someone else also mentioned a WR250 if you are so sold to the brand but the following are wise suggestions. Any of these bikes are a quantum leap from the TT-r, while the 450 based on your excitement of this crash and bike damage tells all of us here you have MUCH to learn yet.
I was in highschool when I first rode my RM125 and now I'm 45, luckily I can still ride, and think my WR450 was a big mistake. I can appreciate it for what it is, but I think unless you are ready to compete seriously it is too much for a play bike. I have already picked up where my KLX300 project was abandoned a few years back to my 450 excitement, as I had much more fun with that bike.
I still park the WR on the trail and look at it being all pretty and impressive, but it is scary fast. I have found myself after nearly 30 years of riding, doing things and going fast enough over things where I know I have fallen and hurt myself really bad, and it magically swallows all this disaster senario up and it is telling you I could have gone over this stuff at twice the speed you woosh!
I have even walked back and looked at an obstacle and told myself there was no way I went over this at this speed and survived to think about it.
But 450s don't do everything for you, experience and more experience does this where iy is working for you without you thinking you have it. It is like second nature.
Those guys at your age when we were yound who were as foolish as you are being now, are not riding anymore. Either they got fed up with pain and expensive injuries or are hurt bad enough they couldn;t throw a leg over the bike any more. Yes back then they went faster.
If you like the look and idea of the bike, and don;t weigh over 250lb, buy a used wr250f and stick a 450 sticker on it. Few can tell anyway. It can still take years and years to be as fast as that 250 can be. Don't let magazines and James Stewart tell you what to do with your life.
And start learning how to fix things on your own. Real riders can take that whole bike into single pieces and back in race ready condition in the evening before the race. If you had the skills and experience you would't even be talking about those repairs. They are like brushing your teeth in the morning.
Before you find offense in what I say, think of all those fools telling you forget that WR get a Husaberg or a KTM 530, they are better. Will they push your wheelchair any faster than I will?
It is not the bike, it is the rider that makes them go fast. If you don;t believe me go find some youtube videos of the early 80s and see how fast you could go with a 125 with 25 year old suspension technology, and how much faster those guys are than you would be on the 450. Look for names like Hannah, Ward, Mikola, Howerton, etc. Wasn't Bailey the one paralized? Hhhmmmm he was fast!
There are a lot of other bikes that would be a real upgrade from your TT-R that you could also consider: KDX-200/220, KLX-300, KTM-200/250, etc.
You can generally find a good, reliable, used bike for a LOT less money if you are willing to do the leg work and to thoroughly inspect the bikes before you buy.