I have a Jackson Coosa HD, its pretty wide and very stable , which allows me to stand up and fish from it. I would suggest getting a larger kayak with a wider base just to feel more comfortable and add much more stability. So I would suggest checking out a Jackson Big Rig, or a Hobie pro Angler. I'm not sure what your budget is but Hobies are very expensive, however they are very wide, spacious, and are pedal propelled. A pro anglers weight capacity is 500lbs. Big Rigs run about $1,700 brand new but I'm sure you could find a pre-owned for around $1k. I think the weight capacity is around 450 lbs. I fish with some bigger guys who have Big rigs and they say it works perfect for them.
If you're on a budget you might check out Ascend kayaks. I don't have much knowledge on them, other than they are supposedly pretty stable and are cheaper for a wide 'stand-up kayak'. The weight capacity on them are 350lbs.
If you are on a budget I would suggest searching through kayak fishing forums for used kayaks, and maybe even Craigslist. If you live near a kayak/canoe dealership, they may have used demos for sale, which is how I bought mine. They may also be able to direct you to someone looking to sell their kayak.Demos are basically brand new, with a few hundred bucks shaved off.
I hoped this will help you out on your search!
Jackson Big Rig
Hobie Pro Angler
Ascend