Are Sec 403(B) plans exempt from providing a fiduciary bond even if the plan is subject to Title I of ERISA?

Yes, the bonding requirements apply to ERISA 403(B) plans as well. An employer must obtain fidelity bond that covers all individuals who handle plan asset. There is an exception if the employer delivers all contributions to an insurer or custodian by the time the employer segregates contributions from the employer's general assets, but as a practical matteran employer would likely wish to purchase protection against fraud by an employee even if not required to do so.

Fortunately, ERISA bonds are quite inexpensive. The size of the bond is the same as for qualified plans 10% of plan assets (valued as of the end of the preceding plan year), up to $500,000.