Thanks to reader Jackie for this tip!
Right now on the Sigma website, you can enter code CHEERS20 to receive 20% off sitewide, including items on the sale page. Free shipping on orders $50+, and there are various freebies that you'll have the option to select in your cart once you hit a certain threshold (you can check them all out HERE).
Jackie said she believes this sale ends at 11:59PM Central on 4/29. I checked around and this code is listed on all of the various coupon websites, but I only saw one reference to an end-date and that particular website said the code is valid until 4/30. To be safe, just try to place your order before midnight Central on 4/29, if you're interested.
Thanks again for the hot tip, Jackie!
PS: Nordstrom will not price-match unless the sale is visible on the homepage of the retailer's website. Since this code is not listed on the Sigma homepage, Nordstrom probably will not price-match (that's been my experience in the past).