The Hirose DF12(5.0)-30DP-0.5V(86) is a 30-position header from the DF12 series, designed for board-to-board mezzanine stacking.
That 5mm gap between the two PCBs is the dimension you design your enclosure around — it's tight enough for a slim handheld case but leaves room for a few passives on the underside of the top board. The 0.50mm pitch means the PCB traces neck down between pads, so your board house needs to handle fine-line routing.
For a BOM line that still calls out the DF12(5.0)-30DP-0.5V(86), the only channel is the surplus and independent distribution market — we source it against an RFQ and confirm availability and current pricing at quote time. If you're designing a new board, look at the current Hirose DF12 series variants; the pitch and stack height are the parameters to match.