Ok well, back on topic.
No leverage bits are allowed in lower level dressage. Any sane person using a pelham is going to be using a mullen mouth pelham. If you are using a jointed or ported pelham then you're going to have a bigger problem on your hands as far as scaling back your bitting just because something with leverage AND pallate pressure is a very severe bit.
My advice would be to work the horse on the lunge in sidereins and a regular french link or double jointed snaffle just to let him get used to a bit again. Hell I'd even ride him in a bitless or halter just to get that bad feeling out of his mouth. Then I'd pick up working him in a really soft bit. It's going to have the same effectiveness, as long as you don't overuse it. If you have really soft hands and don't ever pull, then when you do give an aid with the bit, the contrast between a soft hand and an aiding hand is still going to give him an aid, but this time it's just instead of the contrast between a pulling hand and a pulling harder hand.
If taking time off to rehabilitate the horse isn't possible, or if you are just looking for something to chuck on him for a dressage show then I would look at Baucher or b-ring snaffles. I know they are legal in Canada, not sure about the states, but they are the harshest thing allowed in lower levels. Sprenger Baucher Bit Baucher Bit, Argentan Bahr Saddlery for all your equestrian needs Tack Shop Saddlery Store for Equestrians Horses Equine Products Dressage Hunter Jumper Eventing Supplies Apparel Tack Ontario Canada
WIth the baucher, it just gives the illusion of slight poll pressure to the horse. Just don't use it upside down, because that's illegal too. It's right side up in the picture.
Like spyder said, if he is used to working in a mullen mouth, then don't chnge it up, just find a baucher mullen mouth. However if he is used to a ported or jointed mouth piece then I'd try to find soemthing with either a french link or single joint. Keep as much of the bit the same as possible.