While the spot price of a treasury may vary as interest rates change, a treasury held to maturity will never lose value and always return the full principal and stated interest (if not then we've probably got more to worry about than SIPC insurance!). Not for nothing they refer to that as the "risk free rate" in finance! If you match the tenor of your Treasuries appropriately, losing value isn't a risk.
As far as brokers not offering it, that may certainly be the case. It does make you wonder why not, given that this whole Lloyds insurance stuff and multiple SIPC account spreading actually costs them money and provides little real protection while the LOC actually makes them money. I would maintain that if you're concerned enough about the issue to be a thread participant here, it may be worth shopping around for a broker who did offer it.
