Are there any calcium indicators that don't require probenecid (PBC)?

Yes, the following calcium indicators have improved intracellular retention properties and do not require the use of probenecid:

• Cal-520^® AM
• Cal-590™ AM
• Calbryte™ 520 AM
• Calbryte™ 590 AM
• Calbryte™ 630 AM
• Fura-10™, AM

Note: The aformentioned dyes require much less concentrations 0.2 to 1 mM, compared to Fluo-3 AM and Fluo-4 AM that require concentrations of 2.5 mM.