Q. It became popular in some places to use during Hoshanos on Sukos, when doing Hakofes, a little siddur that one attaches with a type of clip to the basket-holder attached to the Lulav and the Haddassin and Arovos. That is a good way to be able to hold the Lulav and Esrog with both hands (as you wrote that it is required) and the necessary Siddur.
Is that permitted? After all one is using the Lulav as an object to hold that siddur, and it should not be allowed.

A. Horav Shlomo Miller’s Shlit’a opinion is that since he is not attaching the clip directly to the Lulav itself, but only to the basket – holder that serves it, it is permitted.

Others recommend attaching the clip to one’s sleeve.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a