How do I change the route depending on selection in laravel - laravel

Question

I'm trying to create a page that lets the user select a product and then when they press "add to cart" that product then gets sent to the cart page.
On my product page I can have the same item that has 2 or more codes attached to it, so I've created a selection that has the codes and the user then has to pick one of them
and then press "add to cart" button to go to the cart page.
So the way I have it at the moment is that the form grabs the id of the product page and not of the selection box.
What I would like to know is how would I go about changing the route depending on what I've selected.
Here is my code
<form action="{{ route('product.addToCart', ['id' => $product->id]) }}" method="POST">
{{ csrf_field() }}
<div class="row">
<div class="col-lg-12 pl-0">
<select class="form-control mb-2" id="supplier_code" name="supplier_code">
#foreach($parent_product as $parent)
<option value="{{ $parent->supplier_code }}">{{ $parent->supplier_code }}</option>
#if(count($parent->parent))
#foreach($parent->parent as $child)
<option value="{{ $child->supplier_code }}">{{ $child->supplier_code }}</option>
#endforeach
#endif
#endforeach
</select>
</div>
</div>
{{ Form::submit('Add to Cart', array('class' => "btn btn-dark btn-lg btn-block")) }}
</form>
This is my function
public function getAddToCart(Request $request, $id)
{
$menus_child = Menu::where('menu_id', 0)->with('menusP')->get();
$contacts = Contact::all();
$product = Product::find($id);
$supplier_code = $request->supplier_code;
$oldCart = Session::has('cart') ? Session::get('cart') : null;
$cart = new Cart($oldCart);
$cart->add($product, $product->id, $supplier_code);
$request->session()->put('cart', $cart);
return view('public.shopping-cart', ['products' => $cart->items, 'totalPrice' => $cart->totalPrice, 'menus_child' => $menus_child, 'contacts' => $contacts, 'supplier_code' => $supplier_code]);
}
This is my product list page where the user will click on a product to get its details.
<div class="col-xl-9 col-lg-8 col-md-12 product-list">
<div id="parent">
<div class="row grid-container">
#foreach($products as $product)
<?php
$cat_slug = "";
?>
#foreach($product->category as $category)
<?php
$cat_slug .= " ".$category->slug
?>
#endforeach
<?php
$product_image = getImagesArray($product->image);
?>
<div class="product_items col-xl-2 col-lg-4 col-md-4 col-sm-4 {{ $cat_slug }}">
<a href="{!! route('product.item', [$product->slug]) !!}">
<div>
#if(!empty($product_image))
<img src={!! "product_images/products/$product_image[0]" !!}>
#endif
<p>
{!! $product->title !!}
</p>
</div>
</a>
</div>
#endforeach
</div>
</div>
</div>
I'm not sure if I need to add anything else, so if I do need to please let me know

Answer 1

Change this:
<a href="{!! route('product.item', [$product->slug]) !!}">
to this:
<a href="{{ route('product.item', $product->id) }}">