Is there any way to find zip code through user location on roku?

This is very doable but as you and another user said, you need an external api and more importantly, one that is reliable in accuracy.

I can only recommend one api that has been flawless in which I use for weather features on the Roku and web apps.

You can see a demo with the response on page load and get a free api at https://ipstack.com/

Now we add a little bit of. code.

deviceInfo = CreateObject("roDeviceInfo")
ip = deviceInfo.GetExternalIp()
url = "http://api.ipstack.com/" + ip + "?access_key=yourIpStacksApiKey"

m.locationData = createObject("roSGNode", "locationDataReader")
m.locationData.contenturi = url
m.locationData.observeField("content", "locationDataResponse")
m.locationData.control = "RUN"

Create a task

<?xml version = "1.0" encoding = "utf-8" ?>
<component name = "locationDataReader" extends = "Task" >

  <interface>
    <field id = "contenturi" type = "uri" />
    <field id = "content" type = "node" />
  </interface>

  <script type = "text/brightscript" >

    <![CDATA[

     sub init()
       m.top.functionName = "getContent"
     end sub

' **********************************************

    sub getContent()
      apiurl = m.top.url
      m.port = CreateObject ("roMessagePort")
      dataRequest = CreateObject("roUrlTransfer")
      dataRequest.setURL(apiurl)
      dataRequest.EnableEncodings(true)
      https = "https:"
      if LCase(Left(apiurl, Len(https))) = https
        dataRequest.SetCertificatesFile ("common:/certs/ca-bundle.crt")
        'dataRequest.AddHeader ("X-Roku-Reserved-Dev-Id", "")
        dataRequest.InitClientCertificates ()
      end if
      response = dataRequest.getToString()
      'the data will returned as json and you can decide to parse or use regex to get the zipcode
      zipRegex = CreateObject ("roRegex", "zip.:.(\d+).,.latitude", "")
      
      if zipRegex.isMatch(response)
        zipcode = zipRegex.Match(response)
        'if the regex returned data 
        print zipcode
      end if
      'print the whole json response
      print response
    end sub
    ]]>

  </script>

</component>

I don't know if there is a inbuilt way. But, you can use external API. you can find zip code by Passing a IP Address. This is not a good way. Currently, Roku not Blocking any External API may be in Future like IOS. I hope this is helpful