I am size 3-4X and I have a hard time finding nice shirts that fit. I have used Simplicity 9210 size 24 more than once successfully. The pattern has more than one option and it's really not that hard to make. It's in the pattern catalog. I use my hip measurement to pick out the size because that's my plumpest part (!) even though I know you're supposed to use your bust measurement and go from there. Look in the catalogs in the Plus sizes section, you'll find something you like!