I suggest that you continue to tie without a hackle guard. This probably isn't what you wanted to hear, but practice and more practice will eventually show you that they aren't necessary (IMO).
In lieu of a hackle guard, practice using your left fingers (if right handed) to pinch the hackles out of the way while securing them in place and/or finishing the fly. After a while, you may see that the guard would only be a crutch that impedes the development of your manual skills.
My two cents.