Do you need a SPA100?
Serious Programming Adapters are designed for use in GUI development as well as production manufacturing when you need to "burn" your GUI onto the SIM prior to final installation in your product. SPAs are not designed for use directly inside production products.
Many SIMs are cost-optimized and do not have USB Device connectors, JTAG debug connectors, and other features unused in some end products. The JTAG port, for instance, is normally used only for code development and not in a production product. A PCB "gold finger" edge connector on most SIMs carries these signals and a SPA can expose these signals onto readily-usable industry-standard connectors.
For example, the cost-optimized 4.3" SIM225-A03 has the USB device circuit on-board (often used for programming the unit in SHIPTide) but no physical mini-B connector. The SPA100 plugs in the SIM225 and exposes a USB Mini-B connector.