Well, the specifications within ICAO Annex 10, Aeronautical Telecommunications, Volume I - Radio Navigation Aids (November 25, 2016), Chapter 3 - Specifications for radio navigation aids, specifies coverage (as ranges and widths, or as elevation, or as altitude) and as either field strength (in uv/m, microvolts per meter) or energy density (as dBW/m^2, decibel watt per square meter). Hence there are probably a range of common transmission powers, rather than a specific transmission power for each. However, as I would expect navigation aids to typically be placed either on flat terrain or in elevated terrain, there is probably some very common transmission powers.
Edit: Found some data sheets:
ILS [1]
Localizer: Max 20 W (adjustable)
Glideslope: Max 5 W (adjustable)
Marker beacons: Max 2.5 W (adjustable)
VOR [2]
25-100 W in 0.1 W increments
DME [3]
50-106 W (one model)
500-1000 W (another model)
Edit 2: Some minor grammar etc.
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[1] Leonardo Series 2100 Instrument Landing System (ILS) data sheet (PDF, 190 kB) (archived)
[2] Leonardo Model 1150A VHF Omni-Directional Range (VOR) data sheet (PDF, 1.1 MB) (archived)
[3] Leonardo Model 1118A/1119 Distance Measuring Equipment (DME) data sheet (PDF, 441 kB) (archived)