Can I include a clause in the LOI that lets me walk away for any reason at all?

Yes — an explicit unilateral right to walk away, sometimes drafted as a broad termination right requiring no cause at all, can absolutely be negotiated into an LOI, and doing so removes the ambiguity that otherwise exists around whether the non-binding deal terms already give you that freedom. Making it explicit is more protective than relying on the general assumption that price and structure are non-binding, since it addresses directly what happens to everything else in the document if you exercise it.

The complication is how this clause interacts with anything else you've agreed to. A broad walk-away right needs to say clearly whether exercising it also ends your exclusivity commitment, or whether exclusivity continues to run regardless — leaving that unaddressed just creates a new ambiguity in place of the old one. The other side may also resist an unconditional walk-away right without something in exchange, such as reduced exclusivity length or a cost-allocation term addressing their side of the risk.

If you want this kind of protection, have it drafted specifically, with clear treatment of how it interacts with exclusivity and any other binding provisions. A Treadstone business lawyer can negotiate and draft language that actually delivers the flexibility you're looking for.