With Affirm, you can pay over time, 3, 6 or 12 months, starting at 0% interest: 
In addition, PayPal Credit offers PayPal account holders (U.S. only) a 6 month interest-free payment plan. You can apply for this option (subject to approval, which only takes seconds) when checking out online (or call us and we can email you an invoice). IMPORTANT: The email address you use on your order must match the email address associated with your PayPal account.
When online, follow the screenshot instructions here: paypal-website-screenshots-complete.
CareCredit also offers a 6 month interest-free plan with their card. CareCredit orders must be processed over the phone. Please call 888 444 7728 for details.
Finally, CraftOptics accepts any major credit card, or you can use your FSA/HSA card if you have a Flexible Spending Account or Health Savings Account.