One of the best places to find assistive technology or UDL technology is for free with your operating system. Big name brands have figured out there are a lot of people that need them and that number will only grow with an aging population, a greater understanding of the technology, and a greater social acceptance of using this type of technology.
Chrome
Android Accessibility Suite
https://play.google.com/store/apps/details?id=com.google.android.marvin.talkback&hl=en_US
Get started on Android with TalkBack
https://support.google.com/accessibility/android/answer/6283677?hl=en
You have to use the Chrome browser to see this information.
Chrome Web Store - Accessibility - chrome.google.com
https://chrome.google.com/webstore/category/ext/22-accessibility
Turn on Chromebook accessibility features
https://support.google.com/chromebook/answer/177893?hl=en%3Futm_source%3Demail
Google Accessibility
Google has a number of very popular products. This link will give you all of them and the accessibility features you need.
https://www.google.com/accessibility/products-features.html
Grackle
This company makes several products to make Google Suite products more accessible.
https://www.grackledocs.com/pricing-grackle-suite-2/
Grackle Accessibility Checker for G Suite
https://chrome.google.com/webstore/detail/grackle-accessibility-che/copojmaamcpblldileiipebpfjahcnjf?hl=en
Chrome Accessibility
https://chrome.google.com/webstore/category/collection/accessibility
Windows 7
https://www.microsoft.com/enable/products/windows7/
Windows 7 Accessibility Tutorials
https://www.microsoft.com/enable/training/windows7/
Windows 8
https://www.microsoft.com/enable/products/windows8/
Windows 10
https://www.microsoft.com/enable/products/windows10/
Microsoft Accessibility
https://msdn.microsoft.com/en-us/windows/uwp/accessibility/accessibility
Accessibility Apple
This link has considerable information on accessibility for Apple products.
https://www.apple.com/accessibility/
Mac Accessibility
http://www.apple.com/accessibility/osx/
Accessibility iOS
https://www.apple.com/accessibility/iphone/
Apple Watch
http://www.apple.com/accessibility/watch/
Firefox
Firefox
Firefox is one of the most popular browsers. It has a ton of free accessibility features that you can use.
https://support.mozilla.org/en-US/kb/accessibility-features-firefox-make-firefox-and-we
Screen Reader Emulator
This is a screen reader for Firefox.
https://addons.mozilla.org/en-US/firefox/addon/fangs-screen-reader-emulator/
Accessibility for Amazon Fire Tablets and Fire TV
https://www.amazon.com/p/feature/ter2a57g6htm6mr/ref=cm_sw_r_tw__8PwXzbEJD6F8T