You can build the same type of combiner, i.e., Wilkinson combiner/splitter, but using lumped elements.
Every quarterwavelenght transformer is replaced by a low pass lc circuit (Cp1 Ls Cp2).
The 100 ohms resistor will still be there.
Using this idea you can go further and build any hybrid coupler, etc.. and in this way you would need no resistor.
I would personally advise you to build a branchline hybrid using lumped elements . You can probably build very good capacitors in your process. You will need to build spiral inductors.
You should be able to simulate the structure so that you can optimize and tune it in such a way that the parasitic capacitances of the inductors are absorved into the circuit, you will probably need to reduce the lumped capacitors during this optimization.
S.