I found supl-daemon in the maemo Extras repository. Note there is more than one Extras repository -- you may want to look at the chinook extras one. The chinook extras is what I use before there was a diablo Extras to install a-gps and got the supl-daemon installed as a dependency. Once supl-daemon is installed you should be able to install a-gps from a deb and have the dependency met. I'm not an expert on deb packaging but it's my understanding that dependencies met running Application manager won't be necessarily be met with apt-get which is used when you try to directly install a deb package.