Postcode search

I'm a caterer so need to limit my delivery area. There's currently a very ugly map on my page showing my delivery area but I still  field enquiries from people way outside this area. I'm in Sydney, Australia. 

Is there a 3rd party tool or widget that I can use, along the lines of this (which I'm guessing is Wordpress/Shopify;

Grateful for any advice!

We are looking to add a search box where a customer would enter a postcode and it would perform a look up for a post code in a spreadsheet or something. if found a box would appear saying congratulations we have you covered and a button for us to then take details. if not found then it says we are coming to you soon!. which is the best way with limited knowledge.

thanks in advance.

Al

6 minutes ago, alanscully123 said:

We are looking to add a search box where a customer would enter a postcode and it would perform a look up for a post code

Please take a look at my post here and see if this helps to get you started:

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That was great and worked to an extent. I written the html code that works perfectly but only in a browser. ie save the html code to a notepad file then open in chrome.....works great.

When i try and upload it to a page as <code> I think its too many lines as the amount of postcodes lines of  223496 and 3 million characters lol  of them to be exact and  it says error 400. I have hosted the file in google drive and then embedded it to  the page using the google drive link. it says its located the file and get the code error.

Can anyone help?