I am not "for" rewards, but I was getting tired of changing diapers too. I think my ds was slightly older than 3yo. He wasn't feeling the love for pottying in the toilet. lol. I think he was slightly afraid of it. I tried really hard not to make a big deal of it. I mean, I KNEW he'd potty train eventually, and didn't want to pressure him if he wasn't actually ready. But I did want to encourage him, in case he was, kwim?
What I did, was I asked him if he wanted to have a sticker chart for peeing in the potty. He said he did, and I had him help me make it. He decorated it with stickers (everywhere but the actual chart part). When he pee'd (he started out sitting down, btw) he picked a sticker and put it on the chart.
He had stickers he could play with any time he wanted, but these particular stickers (which he picked out to designate as pottying stickers) were only for when he pottied.
When he didn't pee in the potty, I tried really hard not to show disappointment, and just waited until the next time.
He was potty trained really fast. I'm trying to think back, but I think we went through 3 charts (each 1 week) and for the entire last chart he was peeing in the potty every time. He hasn't had any accidents in the day since, and has only had 2 at night.
Imo, part of the reason it worked is because HE was a big part of the sticker chart. It was my idea, and I kinda set the parameters, but he was definitely part of it. He loved the idea of a sticker chart for peeing, and he put the stickers on, etc.
Good luck!