I created a cutom field for the Woocommerce check out page with several items:

add_filter( 'woocommerce_after_order_notes', 'haendler_location_checkout_field' );
function haendler_location_checkout_field( $checkout ) {

woocommerce_form_field( 'haendler_location', array(
    'type'        => 'select',
    'class'       => array('my-field-class form-row-wide'),
    'label'       => __('Händler', 'woocommerce'),
    'required'    => true,
    'options'     => array(
        ''   => __('Bitte wählen Sie einen Händler aus', 'woocommerce' ),
        
        
            'ACC' => __('ACC KG (Hamburg) VAN', 'woocommerce' ),
            'SOMMERDAMM' => __('Autohaus Sommerdamm (Worms) VAN', 'woocommerce' ),
                        
            'EMR' => __('EMR Campers (Stuttgart) WOMO', 'woocommerce' ),
            'THOMA' => __('Eurocar Thoma (Dueren) WOMO', 'woocommerce' ),

            'WVS' => __('WVS Wohnmobilvermietung (Saarlouis) VAN & WOMO', 'woocommerce' ),
            'OWL' => __('Wohnmobil Zentrum OWL (Verl) VAN & WOMO', 'woocommerce' ),
        
    )
), $checkout->get_value( 'haendler_location' ));        
}

Now I would like to show only special items depending on catagory of the products in the cart:

• retailers which sell vans or vans & womos if only vans are in the cart
• retailers which sell womos or womos & vans if only womos are in the cart
• retailers which sell womos & van if vans and womos are in the cart

I tried a lot of variations in the code to realize this but without success. So I hope somebody can helpt me. It would be great.

My last try is someting like this:

add_action( 'woocommerce_after_order_notes', 'get_cat' );
function get_cat( $cat ) {
global $woocommerce;
foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
$_product = apply_filters( 'woocommerce_cart_item_product',  $cart_item['data'], $cart_item, $cart_item_key );
$cat = wc_get_product_category_list( $cart_item['product_id'] ); 
}
}

 // Add the custom checkout field
 add_filter( 'woocommerce_after_order_notes',  'haendler_location_checkout_field' );
 function haendler_location_checkout_field( $checkout ) {
 if($cat == 'Van') {

    $van = array(
            'dealer2'  => " 'NAUTIC' => __('Natic Campers (Vans)', 'woocommerce') ",
            'dealer1'  => " 'EMR' => __('EMR Campers (Vans & Womos)', 'woocommerce') ",
        );

    $options_van = implode(', ', $van);  
}   
    if($cat == 'Womo') {

    $van = array(
            'dealer3'  => " 'HOLIDY' => __('Holidy Camper (Womos)', 'woocommerce') ",
            'dealer1'  => " 'EMR' => __('EMR Campers (Vans & Womos)', 'woocommerce') ",
        );

    $options_van = implode(', ', $van);  
}   
    else {

    $van = array(
            'dealer1'  => " 'EMR' => __('EMR Campers (Vans & Womos)', 'woocommerce') ",
        );

    $options_van = implode(', ', $van);  
};  

woocommerce_form_field( 'haendler_location', array(
    'type'        => 'select',
    'class'       => array('my-field-class form-row-wide'),
    'label'       => __('Händler', 'woocommerce'),
    'required'    => true,
    'options'     => array(
                        $options_van
    )
),  
$checkout->get_value( 'haendler_location' ));   
}

What is wrong? Has someone an idea?