I'm looking for a block that is like the vector sink, however, it does not store samples in an unbounded manor until it is reset. It's a vector sink that stores a fixed item length worth of samples that allows python to get them when it wants. The block should consume samples every time its called by the scheduler whether the block is accessed by python or not.
You want the Probe Signal Vector (gnuradio.blocks.probe_signal_v*) block. If you only want one item/sample use the Probe Signal block. Either version just stores the most recent item(s) and can be sampled at any time with the level() method.
In general, the “Probe” family of blocks continuously update a measurement which can be queried.