A signal generator, a directional coupler and something to measure the power on the reflected port would seem to me to get her done, it is scalar rather then vector analysis, but we have lived with that for years in the ham world.
Maybe one of those AD log amps (You can these on little boards with SMA connectors on ebay? Search on the AD8318), as a detector, about £10.
A directional coupler can be a handful of resistors and a carefully wound balun on a small ferrite ring, or another little £10 board from ebay, not going to be great, but it would serve.
You will need to make up a board with just the antenna and matching network terminated to a suitable connector (Probably SMA?) but otherwise having exactly the geometry you intend to use.
Which just leaves the signal gen,you only need a few mW but it is helpful if the output impedance is reasonably close to 50 ohms.
73 Dan.