UPDATE
Here is the Hex for the Ultraball Canvas backpack: E90B (3049 as UInt16).
Furthermore, I did some digging in my spare time and created a little script to check the minimum and maximum values of the intervals represented by the various fashion groups in the base game, and annotate in a set() the missing IDs (expressed as UInt16). Here's what I found:
Now, doing the conversion in Hex, we see that all the missing bags in the base game have been mapped, since 3075 is the ID of the floral bag and the others from 3047 to 3049 are the IDs of poké/mega/ultraball backpack (all of them are present in special.txt in the previous reply).
The interesting thing resides in the headwears, where , if we exclude the values 5037 and 5038, which are the League and Star sporty cap (also present in special.txt), there is still an additional value of 5039 (AF13 in Hex) which corresponds to a 'Terastal Sporty Cap':
Which could be the next Portal Event. Keep in mind that injecting this hat could result in unexpected online consequences, if not ban itself, since it hasn't been released yet.
Another interesting thing would be reasearching values under the minimum of some categories, given that some of them report as min value x001 (3002 for bags) instead of x000 like some others. I'll make another reply in case of other discoveries.