I don't think you need to give up just yet... a lot depends on what performance level you want across LF to 3GHz.?
If you are OK with about 20dB return loss (maybe even 25dB) at 3GHz and about 0.05dB tracking accuracy, then you could make the simple system suggested by Alan.
However, I think you would have to make it using pairs of 100R 1206 SMD resistors and use SMA connectors with a very low launch inductance. This can be achieved by trimming or filing the SMA centre launcher down almost flush. I'll try and find some 100R 1206 resistors and have a go at making one over the weekend.
If you definitely want N connectors then maybe the most practical option is the buy a used one. Otherwise, I think it will be more challenging to achieve good performance using N connectors.
