There are no fixed coordinates for Sirius Radio satellites. Unlike XM Radio, Sirius Radio satellites travel in parabolic orbits, so their coordinates change with time. You would have to download their orbital element sets (elsets) and calculate the orbits by hand or use a program or other on-line web site for the calculations.
XM Radio uses geostationary satellites, so their positions are fixed. Note that there is also a Swedish company with satellites named Sirius, but these aren’t the same as the Sirius Radio satellites.
Sirius Radio satellites:
Sirius 1, int’l designator 2000-035A
Sirius 2, int’l designator 2000-051A
Sirius 3, int’l designator 2000-077A
All three satellites are in elliptical orbits with an apogee of 47,000 km, a perigee of 24,500 km and an orbital inclination of 63 degrees.
Since the events of 9/11, satellite orbit data has been under tighter control than in the past. There's only one US web location to get it from, and you need to have an account to get the data. A number of on-line satellite position calculators have discontinued operations, since these sites are not allowed to openly share data obtained from US sources.