Budget Phono Stage w/100k Loading for MMs?

The loading on a MM is going to effect the high freq.
If you want to do it right, get a NAB broadcast test disc, which has all the frequencies on it, and you can dial in the loading for your specific cart, so its ruler flat at the high end. Anything else is just a guess. You can use a volt meter measuring the output from your preamp fixed line outputs. used 1K as your reference point or starting point.

J

47K is the industry standard for phono input load so I wouldn't bother looking for one with 100K. In stead, simply find a phono stage that offers whatever else you want (gain, switching, etc) and replace the 47K resistors on the input with 100K. If you are uneasy about soldering or poking around inside your components, any service tech can do this in less than 15 minutes. You can then use "Y" adaptors with resistor loaded RCA plugs if you want to experiment with lower values.