Sounds like you are looking for RHC chips? Nit sure what you mean by "IOC 5s and the 20s" there is no IOC 20 they had a green $25.
As far as $10s and $20s. Most don't play both and will tell you that a $10 chip is not efficient as it is only a x 2 value higher than the $5 chip, but it is your game and run it how you see fit. I too wanted more denoms and pretty colors in play when I joined the forum and shortly after realized that these guys know exactly what they are talking about. If just playing NL holdem woth no split pots other than tied hands... then yup go ahead and play what you want. But if you get into mixed games with lots of split pots it can be a nightmare having more than 3 - 4 denims to account for in the pot.
Again either way that is your choice on how to build YOUR set. As far as the chips, nothing really comes to mind for original $10s and $20s, likely your best bet is going to be finding a chip you like and relabeling it to what you want. Much easier to find a suitable RHC $25, often they are even cheaper than the $5s. The HSI secondary $25 is one of my favorite ever made, many of them have been gobbled up in sets already but seems like there may still be a few floating around.
Best of luck with the serch!
Fellow Chipper Ben
