utube has several videos on getting back on a sit on top kayak. search
“getting back on sit on top kayak”
If you can’t get in your boat by yourself, maybe you should not be paddling alone. However, I have not done an assisted rescue with a sit on top. It would seem that steadying your boat might help you, along with a hand to help pull you up. I agree that taking a class would be a good idea.
If weather is not too hot, wearing a farmer john wet suit provides excellent horizontal floatation. Also, a paddle float under a non-stretch cord attached to your deck on the opposite side of re-entry combined with a rope stirrup gives extra leverage to push up onto deck (facing down). Practice in over your head depth near shore in calm water first. If you miss, you can swim to shore and try again w/o danger. Have someone nearby to help out if you drift, etc. Just in case. It’s like push-ups, you’ll get better with practice. Last suggestion, use a plain front life jacket to avoid snagging a sea kayaking style vest until you gain consistency. Real paddlers always stay near the slowest paddler for safety. That is “old school” courtesy.
You will need a stirrup (roughly 13 feet of flat webbing tied with a water knot to create a loop). A paddle float can add some extra stability for this method, but is not an absolute requirement. You can’t loop the stirrup around a cockpit the way that you can on a sit-inside sea kayak, but you can place your paddle across the top of the kayak. Loop the stirrup around the shaft of the paddle on the opposite side of the kayak. Reach under the kayak and bring the stirrup below the hull to the side of the kayak that you are on. Wrap the stirrup around the paddle shaft on your side of the kayak as many times as needed to create a “stirrup” for you to put your foot in so that you can use your leg to step up onto the kayak - think of using the stirrup to get up on a horse. If you place an inflated paddle float on the paddle blade on the same side of the boat where you are before deploying the stirrup, you will have added support as you step up on the stirrup. Webbing doesn’t float, so if you are worried about losing your stirrup, you can string a small piece of foam or other buoyant material on the stirrup to keep it from going to the bottom. Look for a certified instructor in your area who can work with you to learn and develop these skills.
As is too often the unfortunate case, the OP made a one-time post on 8/19 and hasn’t been back here since then.
Perhaps all the good ideas will help others with similar issues.
Check out this website’s Safety Tip No. 6 - stirrup re-entry…