Hello! My name is Marcelo, based in Amsterdam and I feel like I'm the exact person you need for this job. This kind of short-time tweaks is exactly what I'm looking for.
I've been working for more than 8 years as a web designer/developer. I'm working full-time now, so I'm looking for build a work relationship of this type of work, small tweaks and adjustments to fill my spare time.
I've been working like this for two years with a virtual credit card based in Houston, Texas, making a complete redesign of their app dashboard, hand-coding, responsive CSS3. They were really satisfied with my work, but needed more time so decided to contract a full-time employee. I can send you their contact details for reference about my work.
So, now I have these empty spots of time on my week, and looking to find a client to keep doing that kind of work. I can solve all the problems you have. I can notice from your description that you know exactly what you need and I like these kind of clients.
Please don't hesitate in contacting me if you have any doubts. Looking forward for your answer.