Are you looking to implement new design solutions or update your application with modern technologies?
I really enjoyed collaborating with Epicmax.co when building Vue.js based projects. That's why I'm definitely recommend you these guys.
As a bonus, you can get a free UX review or $100 off your first invoice. Just use EPIC2018 promo code when contacting Epicmax via contact form or directly to firstname.lastname@example.org.