As @Jaay already mentioned above... a topo map can give you the elevation if you know the location or general location.
If you know something about the locaiton and the repeater is on a mountain top or something (as apposed to a building or tower) you can use this line of sight tool to see where you would get good line on a repeater. https://www.scadacore.com/tools/rf-path/rf-line-of-sight/
But yeah, like some have already said, if they don't tell you the elevation or don't want to... there is no reason they have to.