I will go the new chainring route and keep it simple. I didn't know I could get a 24 in 74 BCD. Thinking 50-36-24, that gives me a good spread of choices with my 34-12 cassette. It is just like my compact road cranks with the 24 for loaded hills, I like it.
I started looking for chainrings online and there aren't many places that have much selection, any suggestions.
Peter White Cycles sells TA chainrings. High quality. Expensive. Here is what he says. 38 is the smallest you can use with the Ultegra 6503 crankset in the outer and middle positions. Not 36. Your crank has 130mm bolt circle diameter for the middle and outer positions. 74mm bolt circle diameter for the inner position. Cheapest inner chainring you can find is perfect for the inner position.
"My most popular chainrings are 48 - 38 - 26 and 24 tooth replacements for Shimano's 9 speed Ultegra and 105 triple cranks. This makes for a much better range of gears if you're touring. Most of Shimano's 9 speed cassettes start with a 12 tooth cog, and some start with 11, which is wasted when your largest chainring is 52 teeth and you're carrying a heavy load. Reducing the size of all the chainrings lets you actually use all nine cogs in back. Why have nine speeds if you can't use them all? 48,38,24 shifts very smoothly with the Ultegra 9 speed front derailleur and STI shifters. When you change the size of the outer chainring, you'll need to change the position of the front derailleur. With every tooth reduction, the derailleur needs to be lowered by 2mm."
"For chainrings compatible with Shimano road triple cranksets, like Dura Ace, Ultegra, 105 and Tiagra, scroll down to the TA Alize 130mm rings for the middle and outer positions. Then scroll to the TA Zelito 74mm rings for the inner (triple) position."
"If you are using STI, you'll need to use a Shimano derailleur specifically designed for STI. The Ultegra Triple FD and the IRD Alpine clone of the Ultegra are designed for a 10 tooth difference between the outer and middle chainring. They're more flexible about the difference between the middle and inner ring. The Dura Ace 9 speed Triple FD is designed for a 14 tooth difference between the outer and middle ring. I get frequent requests for 38 tooth rings to replace the middle 42 tooth ring on the Ultegra Triple crank. But the shifting will be very poor if you do that. If you want a 38 in the middle, either change the outer to a 48, or change the FD to a Dura Ace Triple."
Do a search on TA chainrings and you will find Europe sellers. They will be cheaper than Peter White Cycles.