EmberData peekRecord() method

The app I've been putting together looks like a list of stores (with add/edit/delete options), and clicking on a store name takes you to the list of items in that store (again with add/edit/delete). The router:

Router.map(function() {
    this.route('about');
    this.route('stores');
    this.route('shop', function() {
        this.route('items', { path: '/:shop_id/items' });
        this.route('edit', { path: '/:shop_id/edit' });
    });
});

The model:

// app/models/shop.js
import DS from 'ember-data';

export default DS.Model.extend({
  shopName: DS.attr(),
  shopDetails: DS.attr(),
  items: DS.hasMany('item')
});

and:

// app/models/item.js
import DS from 'ember-data';

export default DS.Model.extend({
  itemName: DS.attr(),
  itemDetails: DS.attr(),
  itemPrice: DS.attr(),
  parentShop: DS.belongsTo('shop')
});

Route for the page that displays the list of items is:

// app/routes/shop/items.js
import Ember from 'ember';

export default Ember.Route.extend({
    model(params) {
        return this.get('store').findRecord('shop', params.shop_id, {
            include: 'items'
        });
    }
});

Now as far as I understand before adding an item to a shop I have to call peekRecord():

// app/controllers/shop/items.js
actions: {
    saveItem() {
        let currentShop = this.get('store').peekRecord('shop', /* shop id here */);
        //rest of the code
    }
}

from:

// app/templates/shop/items.hbs
<button type="submit" >Save</button>

The question is, how do I pass the shop id as the second argument for peekRecord()?